Lubricant composition for hydraulic oil

ABSTRACT

The present invention relates to a lubricant composition, and more particularly to a lubricant composition, which has superior oxidation stability and friction characteristics even under harsh conditions of high temperature and high pressure and is thus suitable for use in hydraulic oil. The lubricant composition of the present invention includes a base oil, a liquid olefin copolymer, a phosphorothioate compound, and phosphonium phosphate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Korean PatentApplication No. 10-2019-0023681, filed on Feb. 28, 2019 with the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein in its entirety by reference.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention relates to a lubricant composition, and moreparticularly to a lubricant composition, which has superior oxidationstability and friction characteristics even under harsh conditions ofhigh temperature and high pressure and is thus suitable for use inhydraulic oil.

2. Description of the Related Art

A lubricant is an oily material used to reduce the generation offrictional force on the friction surface of a machine or to dissipatefrictional heat generated from the friction surface. Because of the widevariety of machinery that requires lubrication and the wide variety ofconditions under which such machinery works, lubricants vary in type andquality. Depending on the application thereof, different types of baseoil must be used. In particular, when a lubricant is used for anairplane or an advanced hydraulic system, hydraulic oil having a strongflame-retarding effect is required.

Any type of hydraulic oil used in industrial fields is a medium of powertransmission and plays roles in lubrication, rust prevention, sealingand cooling of respective parts of hydraulic equipment. The hydraulicoil is manufactured by adding additives to base oil, and is largelyclassified into mineral hydraulic oil (petroleum-based hydraulic oil)and synthetic hydraulic oil depending on the type of base oil, synthetichydraulic oil being classified into polyalphaolefin-based hydraulic oiland ester-based hydraulic oil.

Meanwhile, the operating temperature range of hydraulic oil varies, andespecially in the summer, may be 75 to 850 or higher. At suchtemperatures, however, mineral hydraulic oil and polyalphaolefin-basedhydraulic oil generate a lot of oil vapor. The occurrence of such oilvapor causes a problem of increasing the evaporation loss of hydraulicoil, and also promotes the oxidation of hydraulic oil. Hence, it isnecessary to minimize the generation of oil vapor. In particular,mineral hydraulic oil, which accounts for most hydraulic oil, requiresadditional measures to improve oxidation stability due to thecharacteristics of the base feedstock oil. Moreover, since hydraulicsystems are recently becoming more and more sophisticated, hydraulic oilis required to have superior friction characteristics.

Therefore, the present inventors have developed a lubricant compositionfor hydraulic oil, which has superior thermal and oxidation stabilityand is capable of reducing mechanical wear of hydraulic equipment.

CITATION LIST Patent Literature

(Patent Document 0001) Korean Patent No. 10-0201759

(Patent Document 0002) Korean Patent Application Publication No.10-2008-0109015

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theproblems encountered in the related art, and an objective of the presentinvention is to provide a lubricant composition, in which a functionaladditive for friction reduction and an ethylene-alphaolefin liquidrandom copolymer having a high viscosity index are mixed, therebyexhibiting superior friction characteristics, thermal stability andoxidation stability.

Another objective of the present invention is to provide a lubricantcomposition for hydraulic oil, which is capable of reducing themechanical wear of hydraulic equipment and energy consumption whenapplied to hydraulic equipment and of decreasing evaporation loss due tolow changes in the physical properties of hydraulic oil, and thus may beused for a long period of time.

In order to accomplish the above objectives, the present inventionprovides a lubricant composition, comprising a base oil, a liquid olefincopolymer, a phosphorothioate compound, and phosphonium phosphate.

The base oil may be at least one selected from the group consisting ofmineral oil, polyalphaolefin (PAO) and ester.

The liquid olefin copolymer may be prepared by copolymerizing ethyleneand alphaolefin in the presence of a single-site catalyst system, andthe single-site catalyst system preferably includes a metallocenecatalyst, an organometallic compound and an ionic compound.

The liquid olefin copolymer may have a coefficient of thermal expansionof 3.0 to 4.0.

The liquid olefin copolymer may be included in an amount of 0.5 to 30 wt%, and preferably 0.5 to 25 wt %, in the lubricant composition of thepresent invention.

The phosphorothioate compound may be included in an amount of 0.1 to 5.0wt %, and preferably 0.1 to 3.0 wt %, in the lubricant composition.

The phosphonium phosphate may be included in an amount of 0.05 to 3.0 wt%, and preferably 0.1 to 1.5 wt %, in the lubricant composition.

The lubricant composition may have an SRV friction coefficient of 0.1 to0.35 and a traction coefficient of 0.15 to 0.3.

According to the present invention, a lubricant composition includesphosphorothioate, phosphonium phosphate, and an ethylene-alphaolefinliquid random copolymer having a high viscosity index, which are mixedtogether, thereby improving friction characteristics and thermal andoxidation stability, and is capable of reducing the mechanical wear ofhydraulic equipment and energy consumption when applied to hydraulicequipment, thereby maximizing energy-saving effects.

Also, according to the present invention, the lubricant composition haslow changes in the physical properties of hydraulic oil, thus decreasingevaporation loss, and can endure 1000 min or more, and preferably 1200min or more, in an RBOT oxidation stability test (ASTM D2271), therebyenabling the long-term use thereof as hydraulic oil.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, a detailed description will be given of the presentinvention.

The present invention relates to a lubricant composition, which hassuperior oxidation stability and friction characteristics and is thussuitable for use in hydraulic oil. Hence, the lubricant composition ofthe present invention includes a base oil, a liquid olefin copolymer, aphosphorothioate compound, and phosphonium phosphate.

Here, the base oil varies from the aspects of viscosity, heatresistance, oxidation stability and the like depending on themanufacturing method or refining method, but is generally classifiedinto mineral oil and synthetic oil. The API (American PetroleumInstitute) classifies base oil into five types, namely Group I, II, III,IV and V. These types, based on API ranges, are defined in APIPublication 1509, 15^(th) Edition, Appendix E, April 2002, and are shownin Table 1 below.

TABLE 1 Saturated hydrocarbon (%) Sulfur (%) Viscosity index Group I<90 >0.03 80 ≤ VI < 120 Group II ≥90 ≤0.03 80 ≤ VI < 120 Group III ≥90≤0.03 VI ≥ 120 Group IV PAO (Poly Alpha Olefin) Group V Ester & Others

In the lubricant composition of the present invention, the base oil maybe at least one selected from the group consisting of mineral oil,polyalphaolefin (PAO) and ester, and may be any type among Groups I to Vbased on the API ranges.

More specifically, mineral oil belongs to Groups I to III based on theAPI ranges, and mineral oil may include oil resulting from subjecting alubricant distillate fraction, obtained through atmospheric distillationand/or vacuum distillation of crude oil, to at least one refiningprocess of solvent deasphalting, solvent extraction, hydrogenolysis,solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acidcleaning, and white clay treatment; wax isomerized mineral oil; or agas-to-liquid (GLT) oil obtained via the Fischer-Tropsch process.

The synthetic oil belongs to Group IV or V based on the API ranges, andpolyalphaolefin belonging to Group IV may be obtained througholigomerization of a higher alphaolefin using an acid catalyst, asdisclosed in U.S. Pat. Nos. 3,780,128, 4,032,591, Japanese PatentApplication Publication No. Hei. 1-163136, and the like, but the presentinvention is not limited thereto.

Examples of the synthetic oil belonging to Group V include alkylbenzenes, alkyl naphthalenes, isobutene oligomers or hydrides thereof,paraffins, polyoxy alkylene glycol, dialkyl diphenyl ether, polyphenylether, ester, and the like.

Here, the alkyl benzenes and alkyl naphthalenes are usuallydialkylbenzene or dialkylnaphthalene having an alkyl chain length of 6to 14 carbon atoms, and the alkyl benzenes or alkyl naphthalenes areprepared through Friedel-Crafts alkylation of benzene or naphthalenewith olefin. The alkylated olefin used in the preparation of alkylbenzenes or alkyl naphthalenes may be linear or branched olefins orcombinations thereof.

Also, examples of the ester include, but are not limited to, ditridecylglutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyladipate, di-2-ethylhexyl sebacate, tridecyl pelargonate, di-2-ethylhexyladipate, di-2-ethylhexyl azelate, trimethylolpropane caprylate,trimethylolpropane pelargonate, trimethylolpropane triheptanoate,pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate,pentaerythritol tetraheptanoate, and the like.

In the lubricant composition of the present invention, the liquid olefincopolymer is prepared by copolymerizing ethylene and alphaolefinmonomers in the presence of a single-site catalyst system in order touniformly distribute alphaolefin units in the copolymer chain.Preferably, the liquid olefin copolymer is prepared by reacting ethyleneand alphaolefin monomers in the presence of a single-site catalystsystem including a crosslinked metallocene compound, an organometalliccompound, and an ionic compound for forming an ion pair through reactionwith the crosslinked metallocene compound.

Here, the metallocene compound included in the single-site catalystsystem may be at least one selected from the group consisting ofChemical Formulas 1 to 6 below.

In Chemical Formulas 1 to 4,

M is a transition metal selected from the group consisting of titanium,zirconium, and hafnium,

B is absent or is a linking group including a C1-C20 alkylene group, aC6-C20 arylene group, C1-C20 dialkyl silicon, C1-C20 dialkyl germanium,a C1-C20 alkylphosphine group or a C1-C20 alkylamine group,

X₁ and X₂, which are the same as or different from each other, are eachindependently a halogen atom, a C1-C20 alkyl group, a C2-C20 alkenylgroup, a C2-C20 alkynyl group, a C6-C20 aryl group, a C7-C40 alkylarylgroup, a C7-C40 arylalkyl group, a C1-C20 alkylamido group, a C6-C20arylamido group, a C1-C20 alkylidene group or a C1-C20 alkoxy group, and

R₁ to R₁₀, which are the same as or different from each other, are eachindependently hydrogen, a C1-C20 alkyl group, a C2-C20 alkenyl group, aC6-C20 aryl group, a C7-C20 alkylaryl group, a C7-C20 arylalkyl group, aC5-C60 cycloalkyl group, a C4-C20 heterocyclic group, a C1-C20 alkynylgroup, a C6-C20-aryl-containing hetero group or a silyl group.

In Chemical Formulas 5 and 6,

M is a transition metal selected from the group consisting of titanium,zirconium, and hafnium,

B is absent or is a linking group including a C1-C20 alkylene group, aC6-C20 arylene group, a C1-C20 dialkyl silicon, a C1-C20 dialkylgermanium, a C1-C20 alkylphosphine group or a C1-C20 alkylamine group,

X₁ and X₂, which are the same as or different from each other, are eachindependently a halogen atom, a C1-C20 alkyl group, a C2-C20 alkenylgroup, a C2-C20 alkynyl group, a C6-C20 aryl group, a C7-C40 alkylarylgroup, a C7-C40 arylalkyl group, a C1-C20 alkylamido group, a C6-C20arylamido group, a C1-C20 alkylidene group or a C1-C20 alkoxy group, and

R₁ to R₁₀, which are the same as or different from each other, are eachindependently hydrogen, a C1-C20 alkyl group, a C2-C20 alkenyl group, aC6-C20 aryl group, a C7-C20 alkylaryl group, a C7-C20 arylalkyl group, aC5-C60 cycloalkyl group, a C4-C20 heterocyclic group, a C1-C20 alkynylgroup, a C6-C20-aryl-containing hetero group or a silyl group.

Furthermore, all of R₁₁, R₁₃ and R₁₄ are hydrogen, and each of R₁₂radicals, which are the same as or different from each other, mayindependently be hydrogen, a C1-C20 alkyl group, a C2-C20 alkenyl group,a C6-C20 aryl group, a C7-C20 alkylaryl group, a C7-C20 arylalkyl group,a C5-C60 cycloalkyl group, a C4-C20 heterocyclic group, a C1-C20 alkynylgroup, a C6-C20-aryl-containing hetero group or a silyl group.

Also, the metallocene compound of Chemical Formulas 2 to 6 may include acompound substituted through a hydroaddition reaction, and a preferredexample thereof includes dimethylsilyl bis(tetrahydroindenyl) zirconiumdichloride.

The organometallic compound included in the single-site catalyst systemmay be at least one selected from the group consisting of anorganoaluminum compound, an organomagnesium compound, an organozinccompound and an organolithium compound, and is preferably anorganoaluminum compound. The organoaluminum compound may be at least oneselected from the group consisting of, for example, trimethylaluminum,triethylaluminum, triisobutylaluminum, tripropylaluminum,tributylaluminum, dimethylchloroaluminum, dimethylisobutylaluminum,dimethylethylaluminum, diethylchloroaluminum, triisopropylaluminum,triisobutylaluminum, tricyclopentylaluminum, tripentylaluminum,triisopentylaluminum, ethyldimethylaluminum, methyldiethylaluminum,triphenylaluminum, methylaluminoxane, ethylaluminoxane,isobutylaluminoxane and butylaluminoxane, and is preferablytriisobutylaluminum.

The ionic compound included in the single-site catalyst system may be atleast one selected from the group consisting of organoboron compoundssuch as dimethylanilinium tetrakis(perfluorophenyl)borate,triphenylcarbenium tetrakis(perfluorophenyl)borate, and the like.

The component ratio of the single-site catalyst system may be determinedin consideration of catalytic activity, and the molar ratio ofmetallocene catalyst:ionic compound:organometallic compound ispreferably adjusted in the range of 1:1:5 to 1:10:1000 in order toensure desired catalytic activity.

Furthermore, the components of the single-site catalyst system may beadded at the same time or in any sequence to an appropriate solvent andmay thus function as an active catalyst system. Here, the solvent mayinclude, but is not limited to, a hydrocarbon solvent such as pentane,hexane, heptane, etc., or an aromatic solvent such as benzene, toluene,xylene, etc., and any solvent usable in the preparation may be used.

Also, the alphaolefin monomer used in the preparation of the liquidolefin copolymer includes a C2-C20 aliphatic olefin, and mayspecifically be at least one selected from the group consisting ofethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene,4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-octene, 1-decene,1-dodecene and 1-tetradecene, and may include isomeric forms, but thepresent invention is not limited thereto. In the copolymerization, themonomer content is 1 to 95 mol %, preferably 5 to 90 mol %.

The liquid olefin copolymer required in the present invention has acoefficient of thermal expansion of 3.0 to 4.0 and a bromine number of0.1 or less.

The liquid olefin copolymer may be included in an amount of 0.5 to 30 wt%, and preferably 0.5 to 25 wt %, based on 100 wt % of the lubricantcomposition. If the amount of the liquid olefin copolymer is less than0.5 wt % based on 100 wt % of the lubricant composition, stability maydeteriorate. On the other hand, if the amount thereof exceeds 30 wt %,application of the resulting composition to hydraulic oil becomesdifficult, which is undesirable.

The phosphorothioate compound, serving as a friction-reducing agent, maybe at least one selected from the group consisting ofmonophosphorothioate, diphosphorothioate, triphosphorothioate,methylphosphorothioate, ethylphosphorothioate andsulfonylphosphorothioate. When the phosphorothioate compound is includedin the lubricant composition, it may exhibit synergistic effects with anexisting wear-resistant agent and friction reduction effects, andadditionally, energy-saving effects may be achieved through frictionreduction.

The phosphorothioate compound may be included in an amount of 0.1 to 5.0wt %, and preferably 0.1 to 3.0 wt %, based on 100 wt % of the lubricantcomposition. If the amount of the phosphorothioate compound is less than0.1 wt % based on 100 wt % of the lubricant composition, the frictionreduction effect is insignificant. On the other hand, if the amountthereof exceeds 5.0 wt %, the additional reduction effect isinsignificant despite the excessive addition thereof, which isundesirable.

The phosphonium phosphate is a material having the structure of ChemicalFormula 7 below, and is used as a friction/wear-reducing agent. Inparticular, when it is used together with the phosphorothioate compound,the effects thereof may be maximized.

The phosphonium phosphate exists in the form of an ionic liquid havingboth a phosphonium anion and a phosphate cation, and, among variousphosphonium compounds, exhibits a characteristic friction/wear reductioneffect.

Also, the phosphonium phosphate may be included in an amount of 0.05 to3.0 wt %, and preferably 0.1 to 1.5 wt %, based on 100 wt % of thelubricant composition. If the amount of the phosphonium phosphate isless than 0.05 wt % based on 100 wt % of the lubricant composition, thefriction/wear reduction effect may be insignificant. On the other hand,if the amount thereof exceeds 3.0 wt %, there is no synergistic effectthereof with the phosphorothioate compound, and wear may increase, whichis undesirable.

The lubricant composition of the present invention may further includean additive selected from the group consisting of an antioxidant, ametal cleaner, an anticorrosive agent, a foam inhibitor, a pour-pointdepressant, a viscosity modifier, a wear-resistant agent andcombinations thereof.

The antioxidant may be included in an amount of 0.01 to 5.0 wt % basedon 100 wt % of the lubricant composition, and is preferably used in theform of a mixture of a phenolic antioxidant and an aminic antioxidant,more preferably a mixture of 0.01 to 3.0 wt % of the phenolicantioxidant and 0.01 to 3.0 wt % of the aminic antioxidant.

The phenolic antioxidant may be any one selected from the groupconsisting of 2,6-dibutylphenol, hindered bisphenol,high-molecular-weight hindered phenol, and hindered phenol withthioether.

The aminic antioxidant may be any one selected from the group consistingof diphenylamine, alkylated diphenylamine and naphthylamine, andpreferably, the alkylated diphenylamine is dioctyldiphenylamine,octylated diphenylamine, or butylated diphenylamine.

The metal cleaner may be at least one selected from the group consistingof metallic phenate, metallic sulfonate, and metallic salicylate, andpreferably, the metal cleaner is included in an amount of 0.1 to 10.0 wt% based on 100 wt % of the lubricant composition.

The anticorrosive agent may be a benzotriazole derivative, and ispreferably any one selected from the group consisting of benzotriazole,2-methylbenzotriazole, 2-phenylbenzotriazole, 2-ethylbenzotriazole and2-propylbenzotriazole. The anticorrosive agent may be included in anamount of 0 to 4.0 wt % based on 100 wt % of the lubricant composition.

The foam inhibitor may be polyoxyalkylene polyol, and preferably, thefoam inhibitor is included in an amount of 0 to 4.0 wt % based on 100 wt% of the lubricant composition.

The pour-point depressant may be poly(methacrylate), and preferably, thepour-point depressant is included in an amount of 0.01 to 5.0 wt % basedon 100 wt % of the lubricant composition.

The viscosity modifier may be polyisobutylene or polymethacrylate, andpreferably, the viscosity modifier is included in an amount of 0 to 15wt % based on 100 wt % of the lubricant composition.

The wear-resistant agent may be at least one selected from the groupconsisting of organic borates, organic phosphites, organicsulfur-containing compounds, zinc dialkyl dithiophosphate, zinc diaryldithiophosphate and phosphosulfurized hydrocarbon, and preferably, thewear-resistant agent is included in an amount of 0.01 to 3.0 wt %.

The lubricant composition of the present invention has an SRV frictioncoefficient of 0.1 to 0.35. Moreover, the lubricant composition has atraction coefficient of 0.15 to 0.3.

A better understanding of the present invention through the followingexamples. However, the present invention is not limited to theseexamples, but may be embodied in other forms. These examples areprovided to thoroughly explain the invention and to sufficientlytransfer the spirit of the present invention to those skilled in theart.

1. Preparation of Additive Composition

An additive composition for use in the lubricant composition of thepresent invention was prepared as shown in Table 2 below.

TABLE 2 Composi- Composi- Additive composition tion A tion B Antioxidant2,6-dibutylphenol 1 1.5 Diphenylamine 0.8 1 Metal cleaner Metallicphenate 0.2 0.6 Anticorrosive Benzotriazole 0.3 1.0 agent Foam inhibitorPolyoxyalkylene polyol 0.01 0.02 Pour-point Polymethacrylate 0.2 0.5depressant Viscosity Polyisobutylene — 1.0 modifier Wear-resistant Zincdialkyl dithiophosphate 0.2 1.1 agent

2. Preparation of Liquid Olefin Copolymer

A liquid olefin copolymer was prepared using an oligomerization methodthrough a catalytic reaction process. Depending on the reaction time andconditions, which follow, liquid olefin copolymers having differentmolecular weights were prepared, and the properties thereof are shown inTable 3 below.

The reaction time and conditions were increased by 4 hr each from 20 hr.Here, the amounts of hydrogen and comonomer C3, which were addedthereto, were increased by 10% each, and polymerization was performedunder individual conditions, and the resulting polymers were classifieddepending on the molecular weight thereof.

TABLE 3 Main properties Alphaolefin Evaporation Thickening Power (10 CoEof Thermal copolymer Loss (%) wt % in 150N) Expansion Copolymer I 1.28 63.00 to 3.20 Copolymer II 0.54 7 3.20 to 3.40 Copolymer III 0.10 8 3.40to 3.50 Copolymer IV 0.001 10 3.50 to 3.60 Copolymer V 0.0001 12 3.60 to3.70 Copolymer VI 0.00001 14 3.70 to 3.80

3. Preparation of Lubricant Composition for Hydraulic Oil

A lubricant composition was prepared by mixing a base oil, the liquidolefin copolymer, a phosphorothioate compound, phosphonium phosphate andthe additive prepared above, as shown in Tables 4 and 5 below. Here, thebase oil was polyalphaolefin (PAO 4 cSt, available from Chevron Philips)having kinematic viscosity of 4 cSt at 1000, and the phosphorothioatecompound was monophosphorothioate.

Preparation Examples 1 to 67 and Comparative Examples 1 to 14. LubricantComposition for Hydraulic Oil Including Additive A

TABLE 4 Phosphorothioate Alphaolefin Compound Phosphonium CompositionBase oil copolymer Monophosphorothioate phosphate Additive A Preparation97.135 Copolymer 0.1 0.005 2.71 Example 1 I 0.05 Preparation 96.735Copolymer 0.5 0.005 2.71 Example 2 I 0.05 Preparation 95.74 Copolymer1.0 0.5 2.71 Example 3 I 0.05 Preparation 93.74 Copolymer 3.0 0.5 2.71Example 4 I 0.05 Preparation 88.74 Copolymer 5.0 3.5 2.71 Example 5 I0.05 Preparation 96.64 Copolymer 0.1 0.05 2.71 Example 6 I 0.5Preparation 95.74 Copolymer 1.0 0.05 2.71 Example 7 I 0.5 Preparation93.69 Copolymer 3.0 0.1 2.71 Example 8 I 0.5 Preparation 92.09 Copolymer0.1 0.1 2.71 Example 9 I 5 Preparation 91.69 Copolymer 0.5 0.1 2.71Example 10 I 5 Preparation 89.19 Copolymer 3.0 0.1 2.71 Example 11 I 5Preparation 38.29 Copolymer 5.0 4.0 2.71 Example 12 I 5 Preparation86.89 Copolymer 0.1 0.3 2.71 Example 13 I 10 Preparation 86.49 Copolymer0.5 0.3 2.71 Example 14 I 10 Preparation 85.99 Copolymer 1.0 0.3 2.71Example 15 I 10 Preparation 78.79 Copolymer 5.0 3.5 2.71 Example 16 I 10Preparation 76.69 Copolymer 0.1 0.5 2.71 Example 17 I 20 Preparation76.29 Copolymer 0.5 0.5 2.71 Example 18 I 20 Preparation 70.29 Copolymer5.0 2.0 2.71 Example 19 I 20 Preparation 66.29 Copolymer 0.5 0.5 2.71Example 20 I 30 Preparation 60.79 Copolymer 5.0 1.5 2.71 Example 21 I 30Preparation 60.79 Copolymer 0.5 1.0 2.71 Example 22 I 35 Preparation61.19 Copolymer 1.0 0.1 2.71 Example 23 I 35 Preparation 56.79 Copolymer3.0 2.5 2.71 Example 24 I 35 Preparation 53.79 Copolymer 5.0 3.5 2.71Example 25 I 35 Preparation 47.29 Copolymer 10.0  5.0 2.71 Example 26 I35 Preparation 47.235 Copolymer  0.05 0.005 2.71 Example 27 I 50Preparation 46.285 Copolymer 1.0 0.005 2.71 Example 28 I 50 Preparation38.79 Copolymer 5.0 3.5 2.71 Example 29 I 50 Preparation 96.64 Copolymer0.1 0.5 2.71 Example 30 II 0.05 Preparation 95.24 Copolymer 0.5 1.5 2.71Example 31 II 0.05 Preparation 94.24 Copolymer 1.0 2.0 2.71 Example 32II 0.05 Preparation 92.24 Copolymer 3.0 2.0 2.71 Example 33 II 0.05Preparation 90.24 Copolymer 5.0 2.0 2.71 Example 34 II 0.05 Preparation96.19 Copolymer 0.1 0.5 2.71 Example 35 II 0.5 Preparation 93.29Copolymer 3.0 0.5 2.71 Example 36 II 0.5 Preparation 83.79 Copolymer 5.03.5 2.71 Example 37 II 5 Preparation 78.79 Copolymer 5.0 3.5 2.71Example 38 II 10 Preparation 72.285 Copolymer 5.0 0.005 2.71 Example 39II 20 Preparation 97.139 Copolymer 0.1 0.001 2.71 Example 40 III 0.05Preparation 95.24 Copolymer 0.5 1.5 2.71 Example 41 III 0.05 Preparation94.24 Copolymer 1.0 2.0 2.71 Example 42 III 0.05 Preparation 92.24Copolymer 3.0 2.0 2.71 Example 43 III 0.05 Preparation 91.69 Copolymer0.1 0.5 2.71 Example 44 III 5 Preparation 91.29 Copolymer 0.5 0.5 2.71Example 45 III 5 Preparation 76.29 Copolymer 0.5 0.5 2.71 Example 46 III20 Preparation 75.29 Copolymer 1.0 1.0 2.71 Example 47 III 20Preparation 91.19 Copolymer 0.1 1.0 2.71 Example 48 IV 5 Preparation88.29 Copolymer 3.0 1.0 2.71 Example 49 IV 5 Preparation 76.69 Copolymer0.5 0.1 2.71 Example 50 IV 20 Preparation 73.29 Copolymer 3.0 1.0 2.71Example 51 IV 20 Preparation 92.09 Copolymer 0.1 0.1 2.71 Example 52 V 5Preparation 91.69 Copolymer 0.5 0.1 2.71 Example 53 V 5 Preparation78.79 Copolymer 5.0 3.5 2.71 Example 54 V 10 Preparation 77.14 Copolymer0.1 0.05 2.71 Example 55 V 20 Preparation 76.69 Copolymer 0.5 0.1 2.71Example 56 V 20 Preparation 68.79 Copolymer 5.0 3.5 2.71 Example 57 V 20Preparation 45.79 Copolymer 1.0 0.5 2.71 Example 58 V 50 Preparation43.79 Copolymer 3.0 0.5 2.71 Example 59 V 50 Preparation 42.289Copolymer 5.0 0.001 2.71 Example 60 V 50 Preparation 93.64 Copolymer 0.13.5 2.71 Example 61 VI 0.05 Preparation 93.24 Copolymer 0.5 3.5 2.71Example 62 VI 0.05 Preparation 92.74 Copolymer 1.0 3.5 2.71 Example 63VI 0.05 Preparation 92.14 Copolymer 0.1 0.05 2.71 Example 64 VI 5Preparation 91.69 Copolymer 0.5 0.1 2.71 Example 65 VI 5 Preparation77.09 Copolymer 0.1 0.1 2.71 Example 66 VI 20 Preparation 76.29Copolymer 0.5 0.5 2.71 Example 67 VI 20 Comparative 97.24 Copolymer — —2.71 Example 1 I 0.05 Comparative 93.74 Copolymer — 3.5 2.71 Example 2II 0.05 Comparative 87.29 Copolymer — — 2.71 Example 3 II 10 Comparative73.29 Copolymer — 4.0 2.71 Example 4 II 20 Comparative 67.29 Copolymer —— 2.71 Example 5 II 30 Comparative 87.29 Copolymer 5.0 — 2.71 Example 6III 5 Comparative 82.29 Copolymer 5.0 — 2.71 Example 7 III 10Comparative 72.29 Copolymer 5.0 — 2.71 Example 8 III 20 Comparative88.79 Copolymer — 3.5 2.71 Example 9 IV 5 Comparative 87.29 Copolymer5.0 — 2.71 Example 10 IV 5 Comparative 82.29 Copolymer 10.0  — 2.71Example 11 IV 5 Comparative 63.79 Copolymer — 3.5 2.71 Example 12 V 30Comparative 58.79 Copolymer — 3.5 2.71 Example 13 V 35 Comparative 93.74Copolymer — 3.5 2.71 Example 14 VI 0.05

Preparation Examples 68 to 116 and Comparative Examples 15 to 53.Lubricant Composition for Hydraulic Oil Including Additive B

TABLE 5 Phosphorothioate Alphaolefin compound Phosphonium CompositionBase oil copolymer Monophosphorothioate phosphate Additive B Preparation92.58 Copolymer 0.1 0.1 6.72 Example 68 I 0.5 Preparation 92.18Copolymer 0.5 0.1 6.72 Example 69 I 0.5 Preparation 91.68 Copolymer 1.00.1 6.72 Example 70 I 0.5 Preparation 88.08 Copolymer 0.1 0.1 6.72Example 71 I 5 Preparation 87.28 Copolymer 0.5 0.5 6.72 Example 72 I 5Preparation 86.78 Copolymer 1.0 0.5 6.72 Example 73 I 5 Preparation82.68 Copolymer 0.1 0.5 6.72 Example 74 I 10 Preparation 81.78 Copolymer1.0 0.5 6.72 Example 75 I 10 Preparation 79.78 Copolymer 3.0 0.5 6.72Example 76 I 10 Preparation 73.08 Copolymer 0.1 0.1 6.72 Example 77 I 20Preparation 72.28 Copolymer 0.5 0.5 6.72 Example 78 I 20 Preparation71.78 Copolymer 1.0 0.5 6.72 Example 79 I 20 Preparation 92.18 Copolymer0.1 0.5 6.72 Example 80 II 0.5 Preparation 88.78 Copolymer 3.0 1.0 6.72Example 81 II 0.5 Preparation 54.78 Copolymer 5.0 3.5 6.72 Example 82 II30 Preparation 93.08 Copolymer 0.1  0.05 6.72 Example 83 III 0.05Preparation 91.73 Copolymer 0.5 1.0 6.72 Example 84 III 0.05 Preparation91.23 Copolymer 1.0 1.0 6.72 Example 85 III 0.05 Preparation 89.23Copolymer 3.0 1.0 6.72 Example 86 III 0.05 Preparation 86.68 Copolymer0.1 1.5 6.72 Example 87 III 5 Preparation 86.28 Copolymer 0.5 1.5 6.72Example 88 III 5 Preparation 79.78 Copolymer 5.0 3.5 6.72 Example 89 III5 Preparation 74.78 Copolymer 5.0 3.5 6.72 Example 90 III 10 Preparation71.28 Copolymer 0.5 1.5 6.72 Example 91 III 20 Preparation 70.78Copolymer 1.0 1.5 6.72 Example 92 III 20 Preparation 34.78 Copolymer 5.03.5 6.72 Example 93 III 50 Preparation 89.63 Copolymer 0.1 3.5 6.72Example 94 IV 0.05 Preparation 89.23 Copolymer 0.5 3.5 6.72 Example 95IV 0.05 Preparation 86.68 Copolymer 0.1 1.5 6.72 Example 96 IV 5Preparation 83.28 Copolymer 3.0 2.0 6.72 Example 97 IV 5 Preparation79.78 Copolymer 5.0 3.5 6.72 Example 98 IV 5 Preparation 68.28 Copolymer3.0 2.0 6.72 Example 99 IV 20 Preparation 72.68 Copolymer 0.5 0.1 6.72Example 100 IV 20 Preparation 42.68 Copolymer 0.1 0.5 6.72 Example 101IV 50 Preparation 88.13 Copolymer 0.1  0.05 6.72 Example 102 V 5Preparation 87.73 Copolymer 0.5  0.05 6.72 Example 103 V 5 Preparation79.78 Copolymer 5.0 3.5 6.72 Example 104 V 5 Preparation 74.78 Copolymer5.0 3.5 6.72 Example 105 V 10 Preparation 73.08 Copolymer 0.1 0.1 6.72Example 106 V 20 Preparation 71.78 Copolymer 1.0 0.5 6.72 Example 107 V20 Preparation 86.73 Copolymer 3.0 3.5 6.72 Example 108 VI 0.05Preparation 84.73 Copolymer 5.0 3.5 6.72 Example 109 VI 0.05 Preparation87.68 Copolymer 0.5 0.1 6.72 Example 110 VI 5 Preparation 84.28Copolymer 3.0 1.0 6.72 Example 111 VI 5 Preparation 68.28 Copolymer 3.02.0 6.72 Example 112 VI 20 Preparation 61.28 Copolymer 1.0 1.0 6.72Example 113 VI 30 Preparation 39.73 Copolymer  0.05 3.5 6.72 Example 114VI 50 Preparation 42.28 Copolymer 0.5 0.5 6.72 Example 115 VI 50Preparation 38.279 Copolymer 5.0  0.001 6.72 Example 116 VI 50Comparative 68.28 Copolymer 5.0 — 6.72 Example 16 III 20 Comparative58.28 Copolymer 5.0 — 6.72 Example 17 III 30 Comparative 58.18 Copolymer0.1 — 6.72 Example 18 III 35 Comparative 57.78 Copolymer 0.5 — 6.72Example 19 III 35 Comparative 57.28 Copolymer 1.0 — 6.72 Example 20 III35 Comparative 55.28 Copolymer 3.0 — 6.72 Example 21 III 35 Comparative43.18 Copolymer 0.1 — 6.72 Example 22 III 50 Comparative 42.78 Copolymer0.5 — 6.72 Example 23 III 50 Comparative 42.28 Copolymer 1.0 — 6.72Example 24 III 50 Comparative 89.73 Copolymer — 3.5 6.72 Example 25 IV0.05 Comparative 92.23 Copolymer 1.0 — 6.72 Example 26 IV 0.05Comparative 90.23 Copolymer 3.0 — 6.72 Example 27 IV 0.05 Comparative88.23 Copolymer 5.0 — 6.72 Example 28 IV 0.05 Comparative 87.78Copolymer — 0.5 6.72 Example 29 IV 5 Comparative 78.28 Copolymer 10.0  —6.72 Example 30 IV 5 Comparative 83.28 Copolymer — — 6.72 Example 31 IV10 Comparative 78.28 Copolymer 5.0 — 6.72 Example 32 IV 10 Comparative39.78 Copolymer — 3.5 6.72 Example 33 IV 50 Comparative 42.78 Copolymer0.5 — 6.72 Example 34 IV 50 Comparative 42.28 Copolymer 1.0 — 6.72Example 35 IV 50 Comparative 40.28 Copolymer 3.0 — 6.72 Example 36 IV 50Comparative 38.28 Copolymer 5.0 — 6.72 Example 37 IV 50 Comparative93.23 Copolymer — — 6.72 Example 38 V 0.05 Comparative 93.13 Copolymer0.1 — 6.72 Example 39 V 0.05 Comparative 92.73 Copolymer 0.5 — 6.72Example 40 V 0.05 Comparative 92.23 Copolymer 1.0 — 6.72 Example 41 V0.05 Comparative 90.23 Copolymer 3.0 — 6.72 Example 42 V 0.05Comparative 88.23 Copolymer 5.0 — 6.72 Example 43 V 0.05 Comparative84.78 Copolymer — 3.5 6.72 Example 44 V 5 Comparative 69.78 Copolymer —3.5 6.72 Example 45 V 20 Comparative 63.28 Copolymer — — 6.72 Example 46V 30 Comparative 88.28 Copolymer — — 6.72 Example 47 VI 5 Comparative78.28 Copolymer 5.0 — 6.72 Example 48 VI 10 Comparative 58.18 Copolymer0.1 — 6.72 Example 49 VI 35 Comparative 57.78 Copolymer 0.5 — 6.72Example 50 VI 35 Comparative 57.28 Copolymer 1.0 — 6.72 Example 51 VI 35Comparative 55.28 Copolymer 3.0 — 6.72 Example 52 VI 35 Comparative53.28 Copolymer 5.0 — 6.72 Example 53 VI 35

4. Evaluation of Properties

The properties of the lubricant compositions prepared in PreparationExamples and Comparative Examples were measured as follows. The resultsare shown in Tables 6 and 7 below.

Friction Coefficient

In the ball-on-disc mode, friction performance was evaluated bysequentially elevating the temperature in increments of 10□ from 40 to120□ at 50 Hz and comparing the average friction coefficients atindividual temperatures.

Here, the friction coefficient value decreases with an increase ineffectiveness.

Traction Coefficient

The traction coefficient was measured using an MTM instrument made byPCS Instruments. Here, the measurement conditions were fixed at 50N andSRR 50%, and friction and traction were observed depending on changes intemperature. The temperature was varied from 40 to 120□, and the averagevalues were compared.

Wear Resistance

Four steel balls were subjected to friction with the lubricantcomposition for 60 min under conditions of 20 kg load, 1200 rpm, and540, the sizes of wear scars were compared, and evaluation was carriedout in accordance with ASTM D4172. Here, the wear scar (average wearscar diameter, μm) value decreases with an increase in effectiveness.

Oxidation Stability

Oxidation stability was measured using an RBOT (Rotational BombOxidation Test) meter in accordance with ASTM D2271.

TABLE 6 4 Ball Oxidation SRV Friction MTM Traction Wear stabilityCoefficient Coefficient (μm) (RBOT, min) Preparation 0.701 0.598 496 610Example 1 Preparation 0.732 0.569 477 654 Example 2 Preparation 0.7340.587 432 523 Example 3 Preparation 0.735 0.544 501 320 Example 4Preparation 0.712 0.523 665 249 Example 5 Preparation 0.288 0.221 1421580 Example 6 Preparation 0.285 0.200 152 1650 Example 7 Preparation0.265 0.236 133 1600 Example 8 Preparation 0.264 0.219 121 1480 Example9 Preparation 0.267 0.211 110 2000 Example 10 Preparation 0.240 0.236106 2110 Example 11 Preparation 0.736 0.569 511 333 Example 12Preparation 0.246 0.222 116 2420 Example 13 Preparation 0.239 0.207 1231840 Example 14 Preparation 0.257 0.217 140 1680 Example 15 Preparation0.745 0.564 522 285 Example 16 Preparation 0.258 0.213 146 1590 Example17 Preparation 0.259 0.243 147 1510 Example 18 Preparation 0.754 0.555536 278 Example 19 Preparation 0.264 0.222 149 1540 Example 20Preparation 0.768 0.561 555 269 Example 21 Preparation 0.769 0.532 622298 Example 22 Preparation 0.774 0.512 654 277 Example 23 Preparation0.744 0.533 635 279 Example 24 Preparation 0.730 0.612 598 311 Example25 Preparation 0.741 0.633 590 312 Example 26 Preparation 0.745 0.654455 322 Example 27 Preparation 0.756 0.687 478 388 Example 28Preparation 0.725 0.698 497 368 Example 29 Preparation 0.76 0.685 518384 Example 30 Preparation 0.769 0.696 523 368 Example 31 Preparation0.778 0.641 537 321 Example 32 Preparation 0.792 0.621 556 325 Example33 Preparation 0.791 0.632 631 387 Example 34 Preparation 0.269 0.219106 1650 Example 35 Preparation 0.279 0.245 108 1440 Example 36Preparation 0.793 0.612 623 345 Example 37 Preparation 0.797 0.587 647388 Example 38 Preparation 0.755 0.555 612 321 Example 39 Preparation0.702 0.665 678 654 Example 40 Preparation 0.682 0.610 598 523 Example41 Preparation 0.713 0.587 599 320 Example 42 Preparation 0.715 0.588587 333 Example 43 Preparation 0.257 0.219 185 1490 Example 44Preparation 0.259 0.236 168 2110 Example 45 Preparation 0.278 0.217 1351580 Example 46 Preparation 0.279 0.213 108 1490 Example 47 Preparation0.284 0.222 154 1480 Example 48 Preparation 0.231 0.247 163 2456 Example49 Preparation 0.247 0.278 169 2122 Example 50 Preparation 0.264 0.248185 2020 Example 51 Preparation 0.255 0.256 154 1854 Example 52Preparation 0.254 0.219 165 1681 Example 53 Preparation 0.678 0.512 655279 Example 54 Preparation 0.269 0.213 116 1610 Example 55 Preparation0.278 0.243 123 1440 Example 56 Preparation 0.744 0.587 478 347 Example57 Preparation 0.623 0.588 676 348 Example 58 Preparation 0.634 0.521618 384 Example 59 Preparation 0.709 0.569 589 368 Example 60Preparation 0.745 0.587 599 348 Example 61 Preparation 0.725 0.555 568384 Example 62 Preparation 0.756 0.548 534 368 Example 63 Preparation0.284 0.236 147 2410 Example 64 Preparation 0.291 0.245 149 1810 Example65 Preparation 0.264 0.247 108 1560 Example 66 Preparation 0.284 0.256110 1540 Example 67 Comparative 0.721 0.589 454 510 Example 1Comparative 0.759 0.674 505 348 Example 2 Comparative 0.775 0.555 436258 Example 3 Comparative 0.811 0.588 698 412 Example 4 Comparative0.766 0.672 664 510 Example 5 Comparative 0.716 0.521 499 285 Example 6Comparative 0.717 0.569 580 278 Example 7 Comparative 0.726 0.587 590269 Example 8 Comparative 0.725 0.611 510 465 Example 9 Comparative0.691 0.587 651 419 Example 10 Comparative 0.711 0.547 587 322 Example11 Comparative 0.68 0.563 636 249 Example 12 Comparative 0.7 0.587 597321 Example 13 Comparative 0.716 0.539 498 396 Example 14

TABLE 7 4 Ball Oxidation SRV Friction MTM Traction Wear stabilityCoefficient Coefficient (μm) (RBOT, min) Preparation 0.291 0.219 1211660 Example 68 Preparation 0.268 0.209 122 1640 Example 69 Preparation0.269 0.236 132 1490 Example 70 Preparation 0.264 0.221 159 2020 Example71 Preparation 0.247 0.200 164 2110 Example 72 Preparation 0.231 0.236176 2030 Example 73 Preparation 0.255 0.219 157 1650 Example 74Preparation 0.254 0.211 161 1580 Example 75 Preparation 0.251 0.236 1961490 Example 76 Preparation 0.260 0.222 186 1910 Example 77 Preparation0.269 0.207 193 1480 Example 78 Preparation 0.278 0.222 190 1650 Example79 Preparation 0.279 0.219 176 1680 Example 80 Preparation 0.284 0.245189 2020 Example 81 Preparation 0.755 0.587 458 249 Example 82Preparation 0.798 0.639 655 346 Example 83 Preparation 0.768 0.589 636347 Example 84 Preparation 0.736 0.598 664 258 Example 85 Preparation0.747 0.569 673 269 Example 86 Preparation 0.231 0.219 152 1790 Example87 Preparation 0.255 0.211 169 1560 Example 88 Preparation 0.822 0.587676 287 Example 89 Preparation 0.813 0.544 618 288 Example 90Preparation 0.279 0.236 147 2110 Example 91 Preparation 0.278 0.219 1462020 Example 92 Preparation 0.713 0.555 591 412 Example 93 Preparation0.693 0.548 587 322 Example 94 Preparation 0.704 0.512 541 368 Example95 Preparation 0.277 0.245 149 2030 Example 96 Preparation 0.284 0.209198 1650 Example 97 Preparation 0.715 0.555 612 345 Example 98Preparation 0.269 0.256 110 1910 Example 99 Preparation 0.264 0.219 1211480 Example 100 Preparation 0.722 0.589 676 610 Example 101 Preparation0.291 0.236 132 1680 Example 102 Preparation 0.268 0.221 158 1480Example 103 Preparation 0.713 0.532 580 365 Example 104 Preparation0.645 0.555 589 285 Example 105 Preparation 0.255 0.236 194 1610 Example106 Preparation 0.231 0.211 169 1854 Example 107 Preparation 0.758 0.512578 321 Example 108 Preparation 0.759 0.563 579 325 Example 109Preparation 0.251 0.207 154 2080 Example 110 Preparation 0.260 0.234 1692130 Example 111 Preparation 0.261 0.226 226 1780 Example 112Preparation 0.275 0.217 169 1790 Example 113 Preparation 0.813 0.613 501415 Example 114 Preparation 0.734 0.580 512 369 Example 115 Preparation0.784 0.571 523 358 Example 116 Comparative 0.702 0.569 589 299 Example16 Comparative 0.682 0.564 597 388 Example 17 Comparative 0.726 0.512478 347 Example 18 Comparative 0.735 0.533 436 321 Example 19Comparative 0.749 0.523 505 247 Example 20 Comparative 0.748 0.532 518258 Example 21 Comparative 0.725 0.621 556 401 Example 22 Comparative0.704 0.633 623 369 Example 23 Comparative 0.779 0.666 655 358 Example24 Comparative 0.725 0.555 651 269 Example 25 Comparative 0.779 0.563523 388 Example 26 Comparative 0.77 0.611 498 396 Example 27 Comparative0.691 0.587 599 348 Example 28 Comparative 0.711 0.588 568 384 Example29 Comparative 0.716 0.672 647 346 Example 30 Comparative 0.717 0.499698 347 Example 31 Comparative 0.745 0.623 612 299 Example 32Comparative 0.711 0.639 673 519 Example 33 Comparative 0.702 0.598 618654 Example 34 Comparative 0.632 0.569 589 523 Example 35 Comparative0.612 0.587 597 320 Example 36 Comparative 0.643 0.547 591 333 Example37 Comparative 0.756 0.610 698 412 Example 38 Comparative 0.758 0.600678 415 Example 39 Comparative 0.759 0.588 598 369 Example 40Comparative 0.76 0.541 599 358 Example 41 Comparative 0.769 0.563 587347 Example 42 Comparative 0.778 0.522 499 321 Example 43 Comparative0.715 0.543 590 399 Example 44 Comparative 0.749 0.555 587 321 Example45 Comparative 0.646 0.569 523 278 Example 46 Comparative 0.76 0.611 624387 Example 47 Comparative 0.822 0.601 444 412 Example 48 Comparative0.769 0.587 584 345 Example 49 Comparative 0.778 0.588 562 346 Example50 Comparative 0.792 0.541 532 347 Example 51 Comparative 0.791 0.513521 258 Example 52 Comparative 0.793 0.555 511 269 Example 53

As is apparent from Tables 6 and 7, the lubricant compositions includingthe liquid ethylene alphaolefin copolymer, the phosphorothioate compoundand the phosphonium phosphate within the amount ranges of the presentinvention were significantly reduced in wear scar and frictioncoefficient compared to the lubricant compositions of ComparativeExamples, and also exhibited superior oxidation stability. Therefore, itis concluded that the lubricant composition of the present invention isimproved from the aspects of friction characteristics and stability andthus is suitable for use in hydraulic oil.

Although the embodiments of the present invention have been disclosedfor illustrative purposes, those skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible, withoutdeparting from the scope and spirit of the invention as disclosed in theaccompanying claims.

What is claimed is:
 1. A lubricant composition, comprising: 61.28 to96.64% by weight of a base oil, 0.5 to 30% by weight of a liquid olefincopolymer, 0.1 to 3% by weight of a phosphorothioate compound, and 0.05to 2% by weight of phosphonium phosphate, wherein the phosphorothioatecompound is at least one selected from the group consisting ofmonophosphorothioate, diphosphorothioate, triphosphorothioate,methylphosphorothioate, ethylphosphorothioate, andsulfonylphosphorothioate, and wherein the phosphonium phosphate has astructure of Chemical Formula 7 below


2. The lubricant composition of claim 1, wherein the liquid olefincopolymer is prepared by copolymerizing ethylene and alphaolefin using asingle-site catalyst system.
 3. The lubricant composition of claim 2,wherein the single-site catalyst system includes a metallocene catalyst,an organometallic compound and an ionic compound.
 4. The lubricantcomposition of claim 1, wherein the liquid olefin copolymer has acoefficient of thermal expansion of 3.0 to 4.0.
 5. The lubricantcomposition of claim 1, wherein the liquid olefin copolymer has abromine number of 0.1 or less.
 6. The lubricant composition of claim 1,wherein the base oil is at least one selected from the group consistingof mineral oil, polyalphaolefin (PAO), and ester.
 7. The lubricantcomposition of claim 1, further comprising an additive selected from thegroup consisting of an antioxidant, a metal cleaner, an anticorrosiveagent, a foam inhibitor, a pour-point depressant, a viscosity modifier,a wear-resistant agent, and combinations thereof.
 8. The lubricantcomposition of claim 1, wherein the lubricant composition has an SRVfriction coefficient of 0.1 to 0.35.
 9. The lubricant composition ofclaim 1, wherein the lubricant composition has a traction coefficient of0.15 to 0.3.
 10. The lubricant composition of claim 1, wherein thelubricant composition endures 1000 min or more in an oxidation stabilityevaluation (RBOT, ASTM D2271).
 11. The lubricant composition of claim 1,wherein the lubricant composition is used as hydraulic oil.